Fix chart-upgrade as a result of yaml library upgrade

The v3 version of the YAML package used in arkade no longer
parses YAML maps as interface/interface, but string/interface
so introduced regression into the chart upgrade/verify commands.

This commit switches to string/interface{} and fixes the issue.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <[email protected]>

pkg/helm/io.go

@@ -10,7 +10,7 @@ import (
 )
 
 // ValuesMap is an alias for map[string]interface{}
-type ValuesMap map[interface{}]interface{}
+type ValuesMap map[string]interface{}
 
 // Load a values.yaml file and return a ValuesMap with the keys
 // and values from the YAML file as a map[string]interface{}
@@ -22,8 +22,7 @@ func Load(yamlPath string) (ValuesMap, error) {
 
 	values := ValuesMap{}
 
-	err = yaml.Unmarshal(body, &values)
-	if err != nil {
+	if err = yaml.Unmarshal(body, &values); err != nil {
 		return nil, fmt.Errorf("unable to parse %s, error: %s", yamlPath, err)
 	}
 
@@ -51,6 +50,7 @@ func FilterImagesUptoDepth(values ValuesMap, depth int) map[string]string {
 	images := map[string]string{}
 
 	for k, v := range values {
+
 		if k == "image" && reflect.TypeOf(v).Kind() == reflect.String {
 			imageUrl := v.(string)
 			images[imageUrl] = imageUrl